Method and apparatus for changing a digital processing system power consumption state by sensing peripheral power consumption

ABSTRACT

A method and apparatus senses peripheral power consumption for system power control. In a digital processing system, an increase in current drawn by a peripheral device coupled to the digital processing system while the digital processing system is in a reduced power consumption state is sensed, wherein the increase in current drawn provides a current draw detect signal.

RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 09/954,378, filed Sep. 12, 2001 now U.S. Pat. No.6,981,161.

FIELD OF THE INVENTION

The field of the invention relates to sensing of current drawn by aperipheral device in a digital processing system.

BACKGROUND OF THE INVENTION

Most modern computers have a reduced energy consumption mode for energyconservation. One such mode is known as a “sleep” mode. In a sleep mode,all unnecessary components are shut down or put into a minimum powerconsumption mode to save energy, which usually requires a furthersequence a device activation process before they can be used in a normaloperation mode. “Standby” mode is another type of reduced energyconsumption mode which uses even less energy than sleep mode andtherefore requires more time to “wake up.” One example of the operationof a sleep mode can be seen in battery-operated devices, such asnotebook computers. When a notebook computer goes into sleep mode, itshuts down the display screen and disk drive. When the computer is“awakened”, it resumes normal power consumption and operating status.

There are several state-of-the-art approaches to awaken a computer fromsleep mode. The most common way is to awaken the computer upon theuser's moving or clicking a mouse or striking a key on the keyboard.Ethernet “magic packets,” i.e., special bitstreams that wake up thesystem remotely through an Ethernet connection, can also be used.Similarly, a modem ring detect can wake the computer when a call isreceived by its modem. A similar approach uses firewire.

When a machine readable removable media such as a CD-ROM is insertedinto a peripheral device while its computer system is in sleep mode,however, the computer system does nothing. Thus, there is a need forautomatically waking a computer from sleep mode upon the insertion of aremovable media into a peripheral device connected to the computer.

SUMMARY OF THE INVENTION

A method and apparatus senses peripheral power consumption for systempower control. In a digital processing system, an increase in currentdrawn by a peripheral device coupled to the digital processing systemwhile the digital processing system is in a reduced power consumptionstate is sensed, wherein the increase in current drawn provides acurrent draw detect signal.

When a disk is inserted into a drive during a sleep mode, the “diskinsert event” draws significantly more current than during sleep mode.This change in current drawn by the drive can be sensed and a signal canbe provided to the computer system indicating the change. The changesignal can be used to perform a function such as a system wakeup. In oneembodiment, the computer automatically runs the content of the disk orstarts the execution of a preprogrammed operation immediately aftersystem wakeup. For example, if an audio music CD were inserted into thecomputer, the insert event would trigger a wakeup signal and the systemwould then begin to play the music content on the CD automatically afterthe computer woke up.

In one embodiment, the provision of the current draw detect signalrequires no special disk drive. A current sensing mechanism can be addedto a state-of-the-art type of computer system to sense the increasedcurrent drawn by the drive at a disk insert event.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of one embodiment of a method for sensingperipheral power consumption.

FIG. 2 is a flow diagram of one embodiment of a method for sensingincreased current draw by a peripheral device upon insertion of amachine readable removable media into the peripheral device.

FIG. 3 is a flow diagram of one embodiment of a method for detectingautomatically the power supply type of a peripheral device andincreasing the level of power consumed by a digital processing system.

FIG. 4 is a block diagram of one embodiment of a current sensor system.

FIG. 5 is a block diagram of one embodiment of a system with multiplecurrent sensor types.

FIG. 6 is a circuit diagram of one embodiment of a multiple currentsensor system.

FIG. 7 shows one example of a typical computer system which may be usedwith the present invention.

FIG. 8 shows an example of a computer readable media, which may be usedwith the data processing system according to one embodiment of thepresent invention.

DETAILED DESCRIPTION

A method and apparatus senses peripheral power consumption for systempower control. In a digital processing system, an increase in currentdrawn by a peripheral device coupled to the digital processing systemwhile the digital processing system is in a reduced power consumptionstate is sensed, wherein the increase in current drawn provides acurrent draw detect signal.

The term digital processing system will be used interchangeably with theterms computer and computer system. A peripheral device is a deviceattached to a computer. The peripheral device may be an external device,relative to the housing of the computer system, or it may be an internaldevice with the same housing as the computer system. In one embodimentof the invention, a peripheral device which has its current consumptionmonitored is a DVD ROM drive or other optical media drive which iscontained within the housing of a laptop computer, such as a Macintosh™Powerbook™ from Apple™ Computer, Inc. This optical drive may be aslot-loading drive. The terms disk drive, optical disk drive, CD ROMdrive, drive, and peripheral device will be used interchangeably. Itwill be appreciated that other types of peripheral devices (e.g.,CD-RW-ROM drives, Zip™ drives, etc.) may also be used with the presentinvention. Machine readable removable media is software, content orinstructions embodied on a removable media format. The terms machinereadable removable media, removable media, disk, CD, CD-ROM and DVD-ROMwill be used interchangeably. A reduced power consumption state is areduced energy consumption mode for energy conservation. The termsreduced power consumption state, reduced power consumption mode, sleepmode, and standby mode will be used interchangeably. A system wakeup orwakeup is an increase in the level of power consumed by a computersystem from a reduced power consumption state to a higher powerconsumption state. A disk insert event is the perception of a disk beinginserted into a drive as sensed by the increase in current drawn by thedrive. The term wakeup signal will be used interchangeably with theterms wake signal and current draw detect signal.

FIG. 1 is a flow diagram of one embodiment of a method for sensingperipheral power consumption. At block 105, the process begins. At block110 an increase in current drawn by a peripheral device coupled to adigital processing system while the digital processing system is in areduced power consumption state is sensed, wherein the increase incurrent drawn provides a current draw detect signal. At block 125 theprocess ends.

FIG. 2 is a flow diagram of one embodiment of a method for increasingthe level of power consumed by a digital processing system in responseto the insertion of a machine readable removable media into a peripheraldevice coupled to the digital processing system. At block 205, theprocess begins. At block 210, an increase in the current drawn by aperipheral device coupled to a digital processing system when aremovable machine readable media is inserted into the peripheral devicewhile the digital processing system is in a reduced power consumptionstate is sensed, wherein the increase in current drawn provides acurrent draw detect signal. At block 220, the increase in current drawnby the peripheral device is compared against a current consumptionthreshold level with a hysteresis value to verify that an amount thatthe current drawn by the peripheral device has increased is large enoughto merit increasing the level of power consumed by the digitalprocessing system from the reduced power consumption state to a higherpower consumption state. At block 230, noise is filtered from anincrease in the current drawn by the peripheral device to preventimproper increase of the power level consumed by the digital processingsystem. At block 240, the increase in the current drawn by theperipheral device is amplified for more accurate current sensing. Atblock 250, the digital processing system is signaled to exit from thereduced power consumption state in response to the current draw detectsignal. At block 260, the level of power consumed by the digitalprocessing system is increased in response to the current draw detectsignal from a reduced power consumption state to the higher powerconsumption state. In one embodiment, the current drain detect signaldoes not directly wake the system. In another embodiment, the signal isreceived at a wakeup software within the digital processing system. Thewakeup software may, in turn, control the system into a higher powerconsumption state. At block 270, content stored on a removable machinereadable media is retrieved upon the increase in the level of powerconsumed by the digital processing system to the higher powerconsumption state. At block 275, the process ends.

FIG. 3 is a flow diagram of one embodiment of a method for detectingautomatically the power supply type of a peripheral device andincreasing the level of power consumed by a digital processing system.At block 305, the process begins. At block 310, the power supply type ofa peripheral device is detected automatically. At block 320, a desiredcurrent sensor circuitry for the detected power supply type isdetermined based upon the power supply type. At block 330, an increasein the current draw to the peripheral device is sensed with the desiredcurrent sensing circuitry, wherein the increase in current draw providesa current draw detect signal. At block 340, the level of power consumedby the digital processing system is increased in response to the currentdraw detect signal from a reduced power consumption state to the higherpower consumption state. At block 345, the process ends.

In one embodiment, an automatic drive power type detection mechanismdetects the type of power supply of the drive and disables currentsensing circuitry for one or more power supply types when multiple powersupply types are present in the drive. For example, in a drive with a 5Vmain power supply, 5V type current sensing circuitry can detect thecurrent increase caused by the disk insert event and wake up the systemcorrectly. However, in the case of 5V/12V drives, when the drive isoperating in 5V mode it can be very difficult to distinguish a CD insertevent from the normal amount of current flowing to the drive while insleep mode due to noise and other problems. In the case of a multiplepower supply drive, there is no standard for the power supply rail to beused for a disk insert operation. Furthermore, in order to keep thecurrent detect threshold as high as possible with hysteresis, only oneof the power supply rail should be used to detect disk insert operation.This can cause circuit misbehavior and false signals, i.e., falsewakeups. Therefore, in such a case, if the 12V power rail shows currentconsumption above the disk insert operation power threshold level, the5V sensor can be disabled. A more accurate reading can then be obtainedfrom the 12V type sensor. It will be understood by one of ordinary skillin the art that 5V and 12V power supplies are used for the sake ofexample; other power supply types are also possible.

The system may compare a total of 12V and 5V signals to a hysteresisvalue, or compare the signals separately. The hysteresis may have upperand lower trigger points. The lower trigger point is a threshold forentering sleep mode. The upper trigger point is a threshold fordetecting a disk insert event. The hysteresis serves to avoid false diskinsert detects due to noise on the power supply without disturbing thesystem during normal operation. Absent such a hysteresis, the diskinsert detect threshold can be set to a higher level to avoid falsedetects.

FIG. 4 is a block diagram of one embodiment of a current sensor system.Current sensor 410 reads single-voltage type power supply input en routeto a single-voltage type drive. A 5V drive is shown in FIG. 4 as anexample of a single-voltage type drive. Current sensor 410 detects thetotal power consumption of the drive. Current detect and amplify 420receives output from current sensor 410 and detects differences incurrent draw between a reduced power mode and a higher power consumptionmode. Current detect and amplify 420 also amplifies its detected currentdifference. Noise filter 430 filters noise from the reading of change incurrent draw to prevent improper increase of power level consumption orfalse triggering by a noise signal in the power supply. Level detectwith hysteresis 440 has a lower threshold for entering sleep mode and anupper threshold for detecting increased peripheral power consumption,such as at a disk insert event. The hysteresis is used to determinewhether the increase in peripheral power consumption is due to a diskinsert or due to noise on the power supply. Wake signal 450 can be sentto a processor (e.g., a power controller or the system's mainmicroprocessor) to wake the digital processing system from a reducedpower consumption state.

FIG. 5 is a block diagram of one embodiment of a system with multiplecurrent sensor types. In FIGS. 4, 5, and 6, similarly numbered blocksidentify objects having the same function. Drive power detect and diskload detect control 560 determines the power supply type of the driveand disables the current sensor for at least one of multiple powersupply types. In one embodiment, the power supply type detector 560 maybe a redefined pin on an IDE cable, floppy cable, or SCSI cable. Inanother embodiment, drive power detect and disk load detect control 560determines whether a 5V or a 5V/12V drive is present. (These drive typesare exemplary; other drive types are also possible.) If a 5V/12V driveis present, the 5V drive is disabled. The 5V drive may be disconnectedbecause the sensing of the 12V power supply shows a larger differencebetween wake mode and sleep mode. However, the 5V power level reading isnoisy. Therefore, to avoid mistriggering of a wakeup due to noise fromthe 5V power level, the 5V sensing circuitry is disabled. Current sensor510 performs the same function as current sensor 410, but for adifferent power supply type. Logical OR circuit 570 receives input fromeither current sensor 410 or current sensor 510.

In one embodiment, a 12V power supply current reading is translated downto a 5V reading. In order to sense 12V current readings, a 12V powersupply is required in the circuitry. However, the signal that is used totrigger the CPU to wake up the system may need to be 5V. Therefore, the12V signal is translated into a 5V signal or any other voltage thatinterfaces with the system logic (e.g., by a voltage level shifter) tobe delivered to the CPU.

FIG. 6 is a circuit diagram of one embodiment of a multiple currentsensor system. In this embodiment, current sensor 410 senses a 5V powerrail. Current sensor 510 senses a 12V power rail. Logical OR circuit 570receives output from either current sensor 410 or current sensor 510.

FIG. 7 shows one example of a typical computer system which may be usedwith the present invention. Note that while FIG. 7 illustrates variouscomponents of a computer system, it is not intended to represent anyparticular architecture or manner of interconnecting the components, assuch details are not germane to the present invention. It will also beappreciated that network computers and other data processing systemswhich have fewer components or perhaps more components may also be usedwith the present invention. The computer system of FIG. 7 may, forexample, be an Apple Macintosh computer.

As shown in FIG. 7, the computer system 701, which is a form of a dataprocessing system, includes a bus 702 which is coupled to amicroprocessor 703 and a ROM 707 and volatile RAM 705 and a non-volatilememory 706. The microprocessor 703, which may be a G3 or G4microprocessor from Motorola, Inc. or IBM is coupled to cache memory 704as shown in the example of FIG. 7. The bus 702 interconnects thesevarious components together and also interconnects these components 703,707, 705, and 706 to a display controller and display device 708 and toperipheral devices such as input/output (I/O) devices which may be mice,keyboards, modems, network interfaces, printers, and other devices whichare well-known in the art. Typically, the input/output devices 710 arecoupled to the system through input/output controllers 709. The volatileRAM 705 is typically implemented as dynamic RAM (DRAM) which requirespower continually in order to refresh or maintain the data in thememory. The non-volatile memory 706 is typically a magnetic hard driveor a magnetic optical drive or an optical drive or a DVD RAM or othertype of memory system which maintains data even after power is removedfrom the system. Typically, the non-volatile memory will also be arandom access memory, although this is not required. While FIG. 7 showsthat the non-volatile memory is a local device coupled directly to therest of the components in the data processing system, it will beappreciated that the present invention may utilize a non-volatile memorywhich is remote from the system, such as a network storage device, whichis coupled to the data processing system through a network interfacesuch as a modem or Ethernet interface. The bus 702 may include one ormore buses connected to each other through various bridges, controllers,and/or adapters as is well-known in the art. In one embodiment the I/Ocontroller 709 includes a USB (Universal Serial Bus) adapter forcontrolling USB peripherals. Drive 712 is coupled to the system by Drivecontroller 711. Drive controller 711 includes a sensor for sensing thecurrent being drawn by Drive 712, and this sensor produces a currentdraw detect signal when an optical media (e.g., a CD ROM disk) isinserted into the drive 712.

It will be apparent from this description that aspects of the presentinvention may be embodied, at least in part, in software. That is, thetechniques may be carried out in a computer system or other dataprocessing system in response to its processor, such as amicroprocessor, executing sequences of instructions contained in amemory, such as ROM 707, volatile RAM 705, non-volatile memory 706,cache 704, or a remote storage device. In various embodiments, hardwiredcircuitry may be used in combination with software instructions toimplement the present invention. Thus, the techniques are not limited toany specific combination of hardware circuitry and software, nor to anyparticular source for the instructions executed by the data processingsystem. In addition, throughout this description, various functions andoperations are described as being performed by or caused by softwarecode to simplify description. However, those skilled in the art willrecognize that what is meant by such expressions is that the functionsresult from execution of the code by a processor, such as themicroprocessor 703.

FIG. 8 shows an example of a computer readable media which may be usedwith the data processing system according to one embodiment of thepresent invention. The computer readable media contains data andexecutable software which, when executed in the data processing systemsuch as a digital processing system, cause the system to perform thevarious methods of the present invention. As noted above, thisexecutable software and data may be stored in various places including,for example, the ROM 707, the volatile RAM 705, the non-volatile memory706, and/or the cache 704. Portions of this software and/or data may bestored in any one of these storage devices. The media 801, for example,may be primarily the volatile RAM 705 and the non-volatile memory 706 inone embodiment. The user applications 803 represent softwareapplications which are executing on the computer system, such as a wordprocessing application or a spreadsheet application or an Internet webbrowser application. The operating system 807 includes the Open Firmwaresoftware 815 which may be stored in the ROM 707 and loaded into RAM 705at boot up. The loop check software 813 performs the determination ofwhether it is safe to attempt to awaken the digital processing systemfrom a sleep mode. The hardware state software and hardware state value811 is the software which generates the hardware state value. The kernelcode 809 represents the kernel of the operating system and performsnumerous tasks. The virtual memory manager software 821 controls thevirtual memory process. This typically involves maintaining a map ofpage data which represents the state of data in all the virtual memorywhich includes the physical RAM, such as volatile RAM 705 and a portionof the non-volatile memory 706 which has been designated as part of thevirtual memory of the system. The virtual memory manager software willbe performing conventional virtual memory processes as is known in theart. The power manager software 819 performs the various power managingoperations, such as notifying applications and the system and drivers ofchanges to the power consumption state of the system. The software alsomonitors the state of the battery to determine whether sufficient powerexists to continue to operate, and displays alerts to the userindicating the status of the battery and the power status of the system.The disk operating system software 817 performs the conventionalfunctions of a disk operating system. This typically includescontrolling the operation of a hard disk drive which in many examples isthe non-volatile memory 706 which serves as a virtual memory for thevolatile RAM 705. The current sensing software 823 controls the sensingof the current drawn by a peripheral device coupled to the digitalprocessing system. Current sensing software 823 can detect the change incurrent at a disk insert event and decide whether to allow an increasein power consumption (e.g., a user may select an option to not increasepower upon disk insertion and the software can cause the system toignore this event). Power supply type detecting software 825 controlsthe detection of the power supply type of a peripheral device coupled tothe digital processing system. Power supply detecting software 825 cansignal current sensing software 823 to disable one of multiple currentsensors. Hysteresis software 827 compares readings from current sensingsoftware 823 against upper and lower trigger values. Signals fromcurrent sensing software 823 can be used to increase power consumptionof the computer system to a higher power consumption state.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will be evidentthat various modifications may be made thereto without departing fromthe broader spirit and scope of the invention as set forth in thefollowing claims. The specification and drawings are, accordingly, to beregarded in an illustrative sense rather than a restrictive sense.

1. A method in a digital processing system, said method comprisingdetermining at least one of a plurality of power supplies to drive aperipheral device, each power supply being associated with a currentsensor; enabling the current sensor associated with the at least one ofthe plurality of power supplies; sensing an increase in current drawn bythe peripheral device driven by the determined power supplies coupled tothe digital processing system while the digital processing system is ina reduced power consumption state, wherein the increase in current drawnprovides a current draw detect signal.
 2. The method of claim 1, furthercomprising increasing a level of power consumed by the digitalprocessing system in response to the current draw detect signal from thereduced power consumption state to a higher power consumption state. 3.The method of claim 1, wherein the current drawn by the peripheraldevice is increased by an insertion of a removable machine readablemedia into the peripheral device.
 4. The method of claim 2, furthercomprising signaling the digital processing system to exit from thereduced power consumption state in response to the current draw detectsignal.
 5. The method of claim 2, further comprising retrieving contentstored on a removable machine readable media upon increasing the levelof power consumed by the digital processing system to the higher powerlevel consumption state.
 6. The method of claim 5, wherein theretrieving of the content is selected from a group consisting of:playing an audio CD; playing a DVD; and running a computer software. 7.The method of claim 1, wherein the peripheral device is selected from agroup consisting of: a CD-ROM drive; a CD-RW-ROM drive; a DVD-ROM drive;and a floppy disk drive.
 8. The method of claim 1, further comprisingproviding the current draw detect signal to a system power controllersoftware to control power consumption of the digital processing system.9. A method in a digital processing system, said method comprisingsensing an increase in current drawn by a peripheral device coupled tothe digital processing system while the digital processing system is ina reduced power consumption state, wherein the increase in current drawnprovides a current draw detect signal; increasing a level of powerconsumed by the digital processing system in response to the currentdraw detect signal from the reduced power consumption state to a higherpower consumption state; and comparing the increase in current drawn bythe peripheral device against a hysteresis to verify that an amount thatthe current drawn by the peripheral device has increased is large enoughto merit increasing the level of power consumed by the digitalprocessing system from the reduced power consumption state to the higherpower consumption state, wherein, the hysteresis further comprises areduced power level consumption state threshold and a higher power levelconsumption threshold.
 10. A method in a digital processing system, saidmethod comprising sensing an increase in current drawn by a peripheraldevice coupled to the digital processing system while the digitalprocessing system is in a reduced power consumption state, wherein theincrease in current drawn provides a current draw detect signal;increasing a level of power consumed by the digital processing system inresponse to the current draw detect signal from the reduced powerconsumption state to a higher power consumption state; and amplifyingthe increase in the current drawn by the peripheral device for moreaccurate current sensing.
 11. A method comprising: determining at leastone of a plurality of power supplies to drive a peripheral device, eachpower supply being associated with a current sensor; enabling the sensorassociated with the at least one of the plurality of power supplies;sensing an increase in current drawn by the peripheral device driven bythe determined power supplies coupled to a digital processing systemwhile the digital processing system is in a reduced power consumptionstate, the increase caused by insertion of a removable machine readablemedia into the peripheral device; and executing content on the media inresponse to the sensing.
 12. A digital processing system comprising: acontrol circuit coupled to a plurality of power supplies to determine atleast one of the plurality of power supplies to drive a peripheraldevice; a plurality of current sensors coupled to the peripheral devicewhich is coupled to the digital processing system, each current sensorcoupled to a corresponding one of the plurality of power supplies,wherein the current sensor corresponding to the at least one of theplurality of power supplies is enabled according to the control circuit;and a processor coupled to the peripheral device, the current sensordetecting an increase in current drawn by the peripheral device during areduced power consumption mode, the processor, in response to a signalfrom the current sensor, causing the digital processing system to enterinto a higher power consumption mode.
 13. The digital processing systemof claim 12, wherein the sensor detects the increase in current drawn bythe peripheral device upon the insertion of a removable machine readablemedia into the peripheral device.
 14. The digital processing system ofclaim 13, wherein the removable machine readable media is selected froma group consisting of: a audio compact disk; a CD-ROM; a CD-RW-ROM; aDVD-ROM; and a floppy disk.
 15. The digital processing system of claim12, wherein the peripheral device is selected from a group consistingof: a CD-ROM drive; a DVD-ROM drive; and a floppy disk drive.
 16. Adigital processing system comprising a current sensor coupled to aperipheral device which is coupled to the digital processing system; aprocessor coupled to the peripheral device, the current sensor detectingan increase in current drawn by the peripheral device during a reducedpower consumption mode, the processor, in response to a signal from thecurrent sensor, causing the digital processing system to enter into ahigher power consumption mode; and a noise filter to filter out noisefrom input to the current sensor.
 17. A digital processing systemcomprising a current sensor coupled to a peripheral device which iscoupled to the digital processing system; and a processor coupled to theperipheral device, the current sensor detecting an increase in currentdrawn by the peripheral device during a reduced power consumption mode,the processor, in response to a signal from the current sensor, causingthe digital processing system to enter into a higher power consumptionmode, wherein a hysteresis is used for comparison against the increasein the current drawn by the peripheral device to verify that theincrease is large enough to merit causing the digital processing systemto enter into the higher power consumption mode.
 18. The digitalprocessing system of claim 17, wherein the hysteresis further comprisesa reduced power level consumption mode threshold and a higher powerlevel consumption mode threshold.
 19. An article comprising acomputer-readable storage medium having stored thereon a plurality ofinstructions, which if executed by a machine, cause the machine toperform a method, the method comprising: determining at least one of aplurality of power supplies to drive a peripheral device, each powersupply being associated with a current sensor; enabling the currentsensor associated with the at least one of the plurality of powersupplies; and sensing an increase in current drawn by the peripheraldevice driven by the determined power supplies, wherein the increase incurrent drawn provides a current draw detect signal.
 20. The article ofclaim 19, wherein the method further comprises: increasing a level ofpower consumed by the digital processing system in response to thecurrent draw detect signal from a reduced power consumption state to ahigher power consumption state.
 21. The article of claim 19, wherein thecurrent draw to the peripheral device is increased by the insertion of aremovable machine readable media into the peripheral device.
 22. Thearticle of claim 21, wherein the plurality of instructions to beexecuted by the machine further comprise retrieving content stored onthe removable machine readable media upon increasing the level of powerconsumed by the digital processing system to the higher power levelconsumption state.
 23. The article of claim 22, wherein the retrievingof the content is selected from a group consisting of: playing an audioCD; playing a DVD; and running a computer software.
 24. An apparatuscomprising: a determining means for determining at least one of aplurality of power supplies to drive a peripheral device, each powersupply being associated with a current sensor; a enabling means toenable the current sensor associated with the at least one of theplurality of power supplies; a current sensing means for sensing currentdrawn by the peripheral device driven by the determined power suppliescoupled to a digital processing system; and a processing means forincreasing a level of power consumption of the digital processing systemfrom a reduced power consumption mode to a higher power consumption modeupon receipt of a signal from the current sensing means indicating thatthe current drawn by the peripheral device has changed.
 25. Theapparatus of claim 24, wherein the determining means comprises: anautomatic peripheral device power type detecting means for detecting thepower supply type of the peripheral device; and a controlling means forcontrolling a desired sensing means for the detected power supply type.26. The apparatus of claim 24, further comprising an OR logic means forfielding signals issuing from current sensors of one or more powersupply types.
 27. A method for waking a computer from a sleep modecomprising: determining a current consumption threshold for a drive of acomputer, below which threshold the computer is in a sleep mode;enabling detection of current flowing to the drive while the computer isin the sleep mode; and enabling transmission of a wake-up signal to wakethe computer from the sleep mode when the current flowing to the drivewhile the computer is in the sleep mode increases above the currentconsumption threshold for the drive.
 28. The method of claim 27, whereindetermining the current consumption threshold includes determining ahysteresis of the current consumption threshold.
 29. The method of claim28, wherein the hysteresis includes a lower trigger point, below whichthe computer is in the sleep mode, and an upper trigger point, abovewhich transmission of the wake-up signal is enable.
 30. The method ofclaim 27, wherein enabling detection of current flowing to the drivewhile the computer is in the sleep mode includes, when the drive isconnected to more than one power rail, disabling detection of currentflowing to the drive from a lower power rail.
 31. The method of claim30, further comprising redefining a pin on a cable connecting the driveto the computer, said redefined pin enabling detection of multiple powerrails connected to the drive.
 32. The method of claim 27, whereinenabling detection of current flowing to the drive while the computer isin the sleep mode includes, when the drive is connected to more than onepower rail, translating a current reading from a first power rail into asignal for a second, lower, power rail.
 33. The method of claim 27,further comprising enabling amplification of changes in detected currentflow.
 34. An apparatus capable of waking up from a sleep mode, theapparatus comprising: a memory storing instructions for waking up fromthe sleep mode; and a processor coupled to the memory to execute theinstructions from the memory to determine a current consumptionthreshold for a drive of the apparatus, below which threshold theapparatus is in sleep mode, enable detection of current flowing to thedrive while the apparatus is in the sleep mode, and enable transmissionof a wake-up signal to wake the apparatus from the sleep mode when thecurrent flowing to the drive while the apparatus is in the sleep modeincreases above the current consumption threshold for the drive.
 35. Anapparatus capable of waking up from a sleep mode, the apparatuscomprising: a current sensor coupled to a drive of the apparatus; and alogic coupled to the current sensor to process signals from the currentsensor, the logic having a current consumption threshold for the drive,below which threshold the apparatus is in the sleep mode, the logicreceiving data from the signals which indicate current flowing to thedrive while the apparatus is in the sleep mode, and the logic enablingtransmission of a wake-up signal to wake the apparatus from the sleepmode when the current flowing to the drive while the apparatus is in thesleep mode increases above the current consumption threshold for thedrive.
 36. The apparatus of claim 35, wherein the logic determines ahysteresis of the current consumption threshold for the currentconsumption threshold.
 37. The apparatus of claim 35, wherein the logicenables amplification of changes in current flow.